The autophagy protein ATG9A enables lipid mobilization from lipid droplets

AbstractThe multispanning membrane protein ATG9A is a scramblase that flips phospholipids between the two membrane leaflets, thus contributing to the expansion of the phagophore membrane in the early stages of autophagy. Herein, we show that depletion of ATG9A does not only inhibit autophagy but also increases the size and/or number of lipid droplets in human cell lines and C. elegans. Moreover, ATG9A depletion blocks transfer of fatty acids from lipid droplets to mitochondria and, consequently, utilization of fatty acids in mitochondrial respiration. ATG9A localizes to vesicular-tubular clusters (VTCs) that are tightly associated with an ER subdomain enriched in another multispanning membrane scramblase, TMEM41B, and also in close proximity to phagophores, lipid droplets and mitochondria. These findings indicate that ATG9A plays a critical role in lipid mobilization from lipid droplets to autophagosomes and mitochondria, highlighting the importance of ATG9A in both autophagic and non-autophagic processes.

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The Mycobacterium tuberculosis membrane protein Rv0180c: Evaluation of peptide sequences implicated in mycobacterial invasion of two human cell lines

Peptides ◽

10.1016/j.peptides.2010.09.017 ◽

2011 ◽

Vol 32 (1) ◽

pp. 1-10 ◽

Cited By ~ 10

Author(s):

Silvia Marcela Cáceres ◽

Marisol Ocampo ◽

Gabriela Arévalo-Pinzón ◽

Ronald Andrés Jimenez ◽

Manuel Elkin Patarroyo ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Membrane Protein ◽

Cell Lines ◽

Human Cell ◽

Human Cell Lines

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A lipid droplet-peroxisome network drives longevity by monounsaturated fatty acids via modulating ether lipid synthesis and ferroptosis

10.21203/rs.3.rs-740521/v1 ◽

2021 ◽

Author(s):

Anne Brunet ◽

Katharina Papsdorf ◽

Amir Hosseini ◽

Jason Miklas ◽

Matias Cabruja ◽

...

Keyword(s):

Fatty Acids ◽

Lipid Droplet ◽

Lipid Droplets ◽

Unsaturated Fatty Acids ◽

Lipid Synthesis ◽

Ether Lipid ◽

Monounsaturated Fatty Acids ◽

Human Longevity ◽

Ether Lipids ◽

C Elegans

Abstract Dietary mono-unsaturated fatty acids (MUFAs) are linked to human longevity and extend lifespan in several species1-12. But the mechanisms by which MUFAs promote longevity remain unclear. Here we show that an organelle hub involving lipid droplets and peroxisomes is critical for lifespan extension by MUFAs in C. elegans. MUFA accumulation increases lipid droplet number in fat storage tissues, and lipid droplet synthesis is necessary for MUFA-mediated longevity. Interestingly, the number of lipid droplets in young individuals can predict their remaining lifespan. MUFA accumulation also increases the number of peroxisomes, and peroxisome activity is required for MUFA-mediated longevity. By performing a targeted screen, we uncover a functional network between lipid droplets and peroxisomes in longevity. Interestingly, our screen also identifies ether lipids as critical components of the lipid droplet-peroxisome network. Using lipidomics, we find that the ratio of MUFAs to polyunsaturated fatty acids (PUFAs) in ether lipids is increased by MUFA accumulation. Ether lipids are involved in ferroptosis, a non-apoptotic form of cell death13-17, and MUFAs promote longevity in part via suppression of ferroptosis. Our results identify a mechanism of action for MUFAs to extend lifespan and uncover an organelle network involved in the homeostasis of MUFA-rich ether lipids. Our work also opens new avenues for lipid-based interventions to delay aging.

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Deleterious effects of mitochondrial ROS generated by KillerRed photodynamic action in human cell lines and C. elegans

Journal of Photochemistry and Photobiology B Biology ◽

10.1016/j.jphotobiol.2012.08.005 ◽

2012 ◽

Vol 117 ◽

pp. 1-12 ◽

Cited By ~ 35

Author(s):

Toshiharu Shibuya ◽

Yoshihide Tsujimoto

Keyword(s):

Cell Lines ◽

Human Cell ◽

Human Cell Lines ◽

Photodynamic Action ◽

C Elegans ◽

Mitochondrial Ros

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The endoplasmic reticulum-resident protein TMEM-120/TMEM120A promotes fat storage in C. elegans and mammalian cells

10.1101/2021.06.29.450322 ◽

2021 ◽

Author(s):

Yan Li ◽

Siwei Huang ◽

Xuesong Li ◽

Xingyu Yang ◽

Ningyi Xu ◽

...

Keyword(s):

Fatty Acids ◽

Endoplasmic Reticulum ◽

Mammalian Cells ◽

Lipid Droplets ◽

Stimulated Raman Scattering ◽

Transmembrane Helices ◽

Fat Storage ◽

Over Expression ◽

C Elegans

The synthesis of triacylglycerol (TAG) is essential for the storage of excess fatty acids, which can subsequently be used for energy or cell growth. A series of enzymes act in the endoplasmic reticulum (ER) to synthesize TAG, prior to its transfer to lipid droplets (LDs), which are conserved organelles for fat storage. Here, we report that the deficiency of TMEM-120/TMEM120A, a protein with 6-transmembrane helices, retards TAG synthesis and LD expansion in C. elegans. GFP fusion proteins of TMEM-120, expressed at the endogenous level in live worms, were observed throughout the ER network. Using Stimulated Raman Scattering, we demonstrated the specific requirement of TMEM-120 in the storage of exogenous fatty acids in LDs. Knockdown of TMEM120A impedes adipogenesis of pre-adipocytes in vitro, while its over-expression is sufficient to promote LD expansion in mammalian cells. Our results suggest that TMEM-120/TMEM120A plays a conserved role in increasing the efficiency of TAG synthesis.

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Size-Specific Copper Nanoparticle Cytotoxicity Varies between Human Cell Lines

International Journal of Molecular Sciences ◽

10.3390/ijms22041548 ◽

2021 ◽

Vol 22 (4) ◽

pp. 1548

Author(s):

Ina Na ◽

David C. Kennedy

Keyword(s):

Cell Culture ◽

Cell Lines ◽

Copper Nanoparticles ◽

Human Cell ◽

Time Course ◽

Culture Media ◽

Critical Role ◽

Human Cell Lines ◽

Cell Culture Media ◽

Particle Stability

Commercially available copper nanoparticles of three different sizes were tested for cytotoxicity against three human cell lines using four different cytotoxicity assays. This array of data was designed to elucidate trends in particle stability, uptake, and cytotoxicity. The copper nanoparticles are not stable in cell culture media, and rapid changes over the time course of the assays play a critical role in the measured endpoints. Typically, the 40–60 nm particles tested were more cytotoxic than either smaller or larger particles. These particles were also taken up more readily by cells and exhibited different stability dynamics in cell culture media. This provides a good correlation between total cellular uptake of copper and cytotoxicity that may be directly linked to particle stability, though it is unclear why the intermediate-sized particles exhibited these unique properties when compared with both larger and smaller particles.

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ERdj8 governs the size of autophagosomes during the formation process

The Journal of Cell Biology ◽

10.1083/jcb.201903127 ◽

2020 ◽

Vol 219 (8) ◽

Cited By ~ 1

Author(s):

Yo-hei Yamamoto ◽

Ayano Kasai ◽

Hiroko Omori ◽

Tomoe Takino ◽

Munechika Sugihara ◽

...

Keyword(s):

Membrane Protein ◽

Formation Process ◽

Mammalian Cells ◽

Critical Role ◽

Lysosomal Degradation ◽

Membrane Structures ◽

Autophagosome Formation ◽

Paternal Lineage ◽

C Elegans ◽

Atg Proteins

In macroautophagy, membrane structures called autophagosomes engulf substrates and deliver them for lysosomal degradation. Autophagosomes enwrap a variety of targets with diverse sizes, from portions of cytosol to larger organelles. However, the mechanism by which autophagosome size is controlled remains elusive. We characterized a novel ER membrane protein, ERdj8, in mammalian cells. ERdj8 localizes to a meshwork-like ER subdomain along with phosphatidylinositol synthase (PIS) and autophagy-related (Atg) proteins. ERdj8 overexpression extended the size of the autophagosome through its DnaJ and TRX domains. ERdj8 ablation resulted in a defect in engulfing larger targets. C. elegans, in which the ERdj8 orthologue dnj-8 was knocked down, could perform autophagy on smaller mitochondria derived from the paternal lineage but not the somatic mitochondria. Thus, ERdj8 may play a critical role in autophagosome formation by providing the capacity to target substrates of diverse sizes for degradation.

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